Anonymous said the march was about letting “various governments” know that “the free flow of information” will never be stopped. (GARY CAMERON/REUTERS)

Globally, there were significant protests from Canada to Mexico, and from Guatemala to Germany.

Organizers said the march was about letting "various governments" know that "the free flow of information" will never be stopped.

"We now face a dilemma unfamiliar to any previous human civilization, we face this dilemma not simply as a community, nor a nation; rather collectively as a planet," Anonymous said in a promotional video for the event.

Million Mask March protest erupts in London

"We have something no previous generation has ever had, the internet."

There were ugly scenes in central London, where three police officers were injured as protestors threw fireworks and set a patrol car on fire. More than 50 people were arrested on the march, and three men were held in on suspicion of being in possession of offensive weapons.

Police condemned the violence and say they found knives, smoke and paint grenades, gas canisters and lock picks, the BBC reports.

A British police car was set alight as protests turned nasty in London. (JACK TAYLOR/AFP/Getty Images)

"Officers have been hospitalized, a police horse suffered injuries and a police car was criminally damaged during the course of the protest, which is completely unacceptable," said Commander Ben-Julian Harrington.

The dress code for the London march had called for "white judicial wigs, black robes & Anonymous masks for Order of Public Court."

The march was organized for Nov. 5, the UK's "Bonfire Night," which celebrates the capture of Guy Fawkes. Fawkes was a Catholic revolutionary who tried to blow up the Houses of Parliament in 1605 with gunpowder.

Protestors wore the Fawkes masks, originally designed by David Lloyd for the 1988 graphic novel "V for Vendetta," that have been adopted by the Anonymous movement.